1. Field of the Invention
This invention relates to a rolling guide unit adapted to be used for the sliding and rotary portions of a machine tool, various kinds of precision machining apparatuses and a testing apparatus.
2. Description of the Prior Art
A conventional linear motion rolling guide unit consists of a track rail having raceway grooves in the longitudinally extending both side surfaces thereof, a slider saddled on the track rail and having raceway grooves, and a plurality of rolling elements adapted to roll between the opposed raceway grooves, an apparatus of comparatively large weight being placed on the slider, the rolling guide unit being adapted to guide highly precise longitudinal movements of the apparatus over a comparatively long distance (refer to Japanese Patent Laid-Open No. 112021/1989).
FIG. 6 is a perspective view of an example of a conventional linear motion rolling guide unit. As shown in FIG. 6, the linear motion rolling guide unit has two rows of parallel-extending track rails 2 fixed on a bed 20, a plurality of sliders 1 moving slidingly on each track rail 2 in a track rail-saddled state, and a slide table 4 fixed on four sliders 1, one of various kinds of apparatuses placed on the slide table 4 being moved linearly in the longitudinal direction of an arrow G. In this linear motion rolling guide unit, the raceway grooves 5 are formed in the longitudinally extending both side surfaces 21 of the track rails 2, and the slider 1 is mounted on the track rails 2 so as to be slidable thereon in a track rail-saddling state (refer to, for example, Japanese Utility Model Laid-Open No. 23233/1992).
The slider 1 described above is formed as shown in, for example, FIG. 7. FIG. 7 is a perspective view showing an example of a conventional linear motion rolling guide unit. The linear motion rolling guide unit consists mainly of a track rail 2 having raceway grooves 5 in the longitudinally extending both side surfaces 21 thereof, and a slider 1 adapted to be moved linearly on the track rail 2. The slider 1 is placed in a saddled state on the track rail 2, and adapted to be slid freely via a plurality of rolling elements 13 circulating along the raceway grooves 5 in the track rail 2. The slider 1 has a casing 3 provided with raceway grooves 54 in the portions thereof which are opposed to the raceway grooves 5, a plurality of rolling elements 13 fitted between the opposed raceway grooves 5, 54 and consisting of a plurality of circulatingly rollable balls, and end caps 6 attached to both of the longitudinal end portions of the casing 3. The end caps 6 are provided with side seals 50 which attain the sealing of the contact portions of the track rail 2 and slider 1, and a grease nipple 55 for supplying a lubricant to slide surfaces between the track rail 2 and slider 1. In order to prevent the rolling elements 13 from falling from the casing 3, retainer straps 51 are fixed to the casing 3 so as to surround the rolling elements 13. Moreover, in order to reliably prevent the rolling elements 13 from falling from the casing 3, lower seals 53 are fixed to the casing 3 so as to seal the casing 3, the longitudinal extending both side surfaces 21 of the track rail 2 and the lower surface of the casing 3.
The rolling elements 13 in a load region which roll between a raceway groove 5 in the track rail 2 and that 54 in the casing 3 are introduced into a switchover passage (not shown) formed in an end cap 6, and then moved into a return passage 52 formed in the upper portion of the casing 3 and extending in parallel with the raceway groove 54, whereby the rolling elements 13 are circulated limitlessly in the endless circulating passage. Thus, owing to the rolling of the loaded rolling elements 13 positioned between the raceway grooved 54 formed in the slider 1 and those 5 formed in the track rail 2, the slider 1 can be moved linearly on the track rail 2 (refer to, for example, Japanese Patent Application No. 326317/1991).
There is a publication disclosing a conventional rotary motion guide unit shown in FIG. 8 in which a bearing is provided. In this rotary motion rolling guide unit, a bearing 28 formed by inserting cylindrical rollers 32 between an inner race 27, which has a V-shaped raceway surface for making relative movement of the rollers 32 thereon, and outer races 16, 17 is incorporated and a rotary body 24 is fixed rotatably to a base 23. In the rotary motion rolling guide unit, the inner race 27 is fixed to the outer circumferential surface 22 of a cylindrical shaft portion 19 of the base 23 with a fixing means, such as a bolt and a clamp. The rotary body 24 is adapted to be rotated relatively to the base 23, and the upper and lower outer races 16, 17 are fixed to the inner circumferential surface 25 of a cylindrical portion 18 of the rotary body 24 with a fixing means, such as a bolt and a clamp. The rolling guide unit is formed by arranging a plurality of cylindrical rollers 32 in an alternately crossing manner between the inner and outer races 27, 16, 17. The inner race 27 is provided on its outer circumferential side with a V-shaped raceway surface 29, and the upper and lower outer races 16, 17 on their inner circumferential sides with raceway surfaces 30, 31 respectively, by which one V-shaped raceway surface is formed.
There is a publication disclosing a linear motion rolling guide unit as a conventional rolling guide unit, on which an apparatus of comparatively large weight is placed as shown in FIG. 6, the guide unit being adapted to guide a linear longitudinal movement of the apparatus over a comparatively long distance. There is also a publication disclosing a pivotal rolling guide unit in which a bearing 28 is incorporated between a base 23 and a rotary body 24 as shown in FIG. 8, with the rotary body 24 fixed to the base 23 rotatably so that the rotary body 24 can be moved relatively to the base 23. When it is necessary that both a linear movement and a rotational movement be made in a rolling guide unit in accordance with the conventional techniques, the above-mentioned linear motion rolling guide unit and rotary motion rolling guide unit are combined so that both of these movements can be made.
However, a rolling guide unit having construction which enables both a linear movement and a rotational movement to be made simultaneously has not been developed up to the present time. In a conventional structure in which a linear motion guide unit and a rotary motion rolling guide unit are combined, the dimensions of the guide unit increases to a high level, and the height thereof becomes excessively large, or an accumulated error due to the guide unit-combining operation increases. Thus, it is impossible at present to provide a highly accurate rolling guide unit.